Such valve devices are used, for example, for controlling a recirculated exhaust gas flow in an internal combustion engine for the purpose of reducing pollutants in the exhaust gas. The spring element provides that the valve-closing member is pressed on the corresponding valve seat. Depending on the installation site of the exhaust gas recirculation valve immediately behind the exhaust gas outlet of the cylinder or in the region of the intake pipe, in the low-pressure line or the high-pressure line, upstream or downstream of an exhaust gas cooler, the exhaust gas recirculation valve is exposed to different loads. A high thermal load, for example, exists in the immediate vicinity of the exhaust gas outlet of the cylinder, whereas a rather strong sooting tendency can be expected downstream of an exhaust gas cooler.
Two-way valves are also known via which a controlled exhaust gas flow can be directed selectively through an exhaust gas cooler or a bypass duct so that a valve situated downstream of the exhaust gas cooler is sometimes exposed to hot exhaust gas and sometimes to cold exhaust gas, depending on the exhaust gas recirculation line used.
A valve of this type is described, for example, in DE 197 33 964 A1. This valve is arranged downstream of an exhaust gas cooler or a bypass duct and comprises an actuator by which a valve rod can be displaced on which two valve-closing members are slidably arranged. A spring is disposed between the valve-closing members, by which the valve-closing members are biased against stops formed on the valve rod. Both valve-closing members are conical in shape and, in the non-actuated state, are caused by the spring pressure to contact corresponding valve seats. When the actuator is actuated, one of the valve-closing members, depending on the direction, is lifted from the valve seat by the stop against the spring force, whereas the other valve-closing member is still pressed against the valve seat by the spring force. It is thus possible to selectively control the flow-through section of the bypass duct or of the exhaust gas cooler outlet, depending on the direction of actuation. However, the spring disposed centrally in the flow-through region is exposed to high thermal loads and to occurring soiling.
EP 1 859 156 B1 describes a valve device wherein the spring of a correspondingly designed valve is surrounded by a compensation element in the form of a bellows, the axial ends of which are connected with the valve plates. This element is intended to generate a vacuum in the space enclosed thereby so that both valve plates can be lifted from their valve seats at the same time. The bellows may protect the spring and the valve rod area against soiling, however, it no longer functions under high thermal loads.